5 / 20
A straight line from A (53°N, 155°W) to B (53°N, 170°E) is drawn on a Lambert Conformal conical chart with standard parallels at 50°N and 56°N. When passing the meridian 175°E, the True Track is:
  • A
    100.0°
  • B
    257.5°
  • C
    102.5°
  • D
    260.0°

Refer to figure.

Lambert chart: Convergency = Change of longitude º x Convergence factor

Where convergence factor equals sin of Parallel of Origin.

Parallel of Origin: half way between standard parallels - in this case, standard parallels 50ºN and 56ºN => Parallel of origin is 53ºN

Convergence factor = Sin 53º = 0.7986

  • Both points are on latitude 53ºN. Therefore, RLT = 270ºT

  • Difference between RLT and GCT = Conversion Angle

First Step: Calculate GCT at B (from RLT at B and Conversion Angle)

At B
Conversion angle = 1/2 change of longitude x convergence factor

= 1/2 (35º) x 0.7986 = 13.98º (approx. 14º)

GCT at B = RLT - Conversion angle = 270º - 014º = 256º

Second Step: using convergency, use GCT at B to calculate GCT at 175ºE

Convergency = change of longitude x convergence factor

= 5º x 0.7986 = 4º

  • GCT at 175ºE > GCT at B

  • At 175ºE = GCT at B + Convergency

GCT = 256º + 004º = 260º

Your Notes (not visible to others)



This question has appeared on the real examination, you can find the related countries below.

  • United Kingdom
    5
  • Poland
    4
  • Austro Control
    3
  • Ireland
    3
  • Hungary
    1
  • Iceland
    1
  • Pakistan
    1
Keyboard Shortcut Use Keyboard Shortcuts